The foreign body response is an immune-mediated reaction that impacts the fidelity of implanted biomedical devices (Anderson et al., Semin. Immunol. 20:86-100 (2008); Langer, Adv. Mater. 21:3235-3236 (2009); Ward, J. Diabetes Sci. Technol. Online 2:768-777 (2008); Harding & Reynolds, Trends Biotechnol. 32:140-146 (2014)). Macrophage recognition of biomaterial surfaces in these devices initiate a cascade of inflammatory events that result in the fibrous and collagenous encapsulation of these foreign materials (Anderson et al. (2008); Ward (2008); Harding & Reynolds (2014); Grainger, Nat. Biotechnol. 31:507-509 (2013); Williams, Biomaterials 29:2941-2953 (2008)). This encapsulation, over time, often leads to device failure and can result in discomfort for the recipient (Anderson et al. (2008); Harding & Reynolds (2014); Williams (2008)). These adverse outcomes emphasize the critical need for biomaterials that do not elicit foreign body responses to overcome this key challenge to long-term biomedical device function.
The foreign body response to implanted biomaterials is the culmination of inflammatory events and wound-healing processes resulting in implant encapsulation (Anderson et al. (2008)). The final pathological product of this response is fibrosis, which is characterized by the accumulation of excessive extracellular matrix at sites of inflammation and is a key obstacle for implantable medical devices as the cellular and collagenous deposition isolate the device from the host (Anderson et al. (2008); Wick et al., Annu. Rev. Immunol. 31:107-135 (2013); Wynn & Ramalingam, Nat. Med. 18:1028-1040 (2012)). This device isolation can interfere with sensing of the host environment, lead to painful tissue distortion, cut off nourishment (for implants containing living, cellular components), and ultimately lead to device failure. Materials commonly used for medical device manufacture today elicit a foreign body response that results in fibrous encapsulation of the implanted material (Langer (2009); Ward (2008); Harding & Reynolds (2014); Williams (2008); Zhang et al., Nat. Biotechnol. 31:553-556 (2013)). Overcoming the foreign body response to implanted devices could pave the way for implementing new medical advances, making the development of materials with both anti-inflammatory and anti-fibrotic properties a critical medical need (Anderson et al. (2008); Langer (2009); Harding & Reynolds (2014)).
Macrophages are a key component of material recognition and actively adhere to the surface of foreign objects (Anderson et al. (2008); Ward (2008); Grainger, Nat. Biotechnol. 31:507-509 (2013); Sussman et al., Ann. Biomed. Eng. 1-9 (2013) (doi:10.1007/s10439-013-0933-0)). Objects too large for macrophage phagocytosis initiate processes that result in the fusion of macrophages into foreign-body giant cells. These multi-nucleated bodies amplify the immune response by secreting cytokines and chemokines that result in the recruitment of fibroblasts that actively deposit matrix to isolate the foreign material (Anderson et al. (2008); Ward (2008); Rodriguez et al., J. Biomed. Mater. Res. A 89:152-159 (2009); Hetrick et al., Biomaterials 28:4571-4580 (2007)). This response has been described for materials of both natural and synthetic origins that encompass a wide range of physicochemical properties, including alginate, chitosan, dextran, collagen, hyaluronan, poly(ethylene glycol) (PEG), poly(methyl methacrylate) (PMMA), poly(2-hydroxyethyl methacrylate) (PHEMA), polyurethane, polyethylene, silicone rubber, Teflon, gold, titanium, silica, and alumina (Ward (2008); Ratner, J. Controlled Release 78:211-218 (2002)).
The development of implantable devices that resist host foreign body responses for protracted periods of time is important for improving the performance and safety of such devices, and remains an unmet need.
Accordingly, the search for materials of clinical relevance that address the foreign body response to implantable devices, i.e., ameliorate biocompatibility, remains an area of active research.
Therefore, it is an object of the invention to provide polymers for encapsulating and implanting cells, where the polymers have greater biocompatibility following implantation.
It is another object of the invention to provide polymers for modifying the surface of a product to impart a beneficial effect to the product compared to a corresponding product that lacks the polymers.
It is also an object of the invention to provide methods for encapsulating cells using polymers.
It is also an object of the invention to provide methods for modifying the surface of a product using polymers, where the modified product has improved biocompatibility compared to a corresponding product that lacks the polymers.